Cochlear implants have been used clinically to help deaf patients. In addition, the cochlear implant has proven to be an useful tool in assisting researchers in understanding the mechanisms of auditory processing and perception. In order to improve cochlear implant design and efficiency, studies have examined the features of the electrical stimulus and how they effect electrically-induced hearing. One particularly effective variable is electrode configuration. The proposed study will examine neural coding in response to electrical stimulation of the deafened inner ear. Specifically, the effects of electrode configurations on psychophysical and single-unit thresholds will be examined using a guinea pig model. The first specific aim will determine the characteristics of the guinea pig model using psychophysical and inferior colliculus single-unit data. The second specific aim will compare the neuronal spatial single unit response pattern in the inferior colliculus to the psychophysical data. These studies will give insight to how an auditory signal is processed in the auditory pathway under different electrode configurations, and will help in the understanding of why electrode configuration has strong effects on perception.